Electric furnace.



M. J. JOHNSON.

ELEGTRIU FURNACE. APPLICATION FILED DEO.1,1910.

1335,596. Patented Aug. 13,1912.

INVENTOR BY v ATTORNEY UNITED STATES MANFRED J. "JOHNSON, OF NAUGA TUCK,CONNECTICUT.

ELECTRIC FURNACE.

Specification of Letters Patent.

Application filed December 1, 1910. Serial No. 595,083.

T 0 all whom it may concern i Be it known that I, MANFRED J. J OHNSON, acitizen of the United States, residing at Naugatuck, county of NewHaven, State of Connecticut, have invented an Improvement in ElectricFurnaces, of which the following is a specification.

This invention has for its object to provide an electric furnace ormutlle adapted for general. use and especially adapted for the-hardeningof tools and for dentists use and for the making and repairing of smallmetallic articles, which shall be less expensive to produce and far moredurable than any furnace of this class heretofore placed upon themarket. 4

Vith these and other objects in view the invention consists in certainconstructions and in certain parts, improvements and combinations whichwill be hereinafter described and then'sp'ccifically pointed out in theclaims hereunto appended.

In the accompanying drawing forming a part of this specification, Figure1 is a side elevation of my novel furnace; Fig. 2 an elevation as seenfrom the right in Fig.

1; Fig. 3 a longitudinal section on an snlarged scale; and Fig. l is atransverse section on the line 4.4 in Fig. 3, looking in the directionof the arrows.

10 denotes the body of my rovcl furnace or muffle, which is shown ascarried by an arm 11 which may be attached to any suitable fixture inconvenient position for ire. In the present instance I have .ilOWIl thearm as secured to a transformer indicated by '12.

13 denotes binding posts for-the attachment of line wires, 1'4 a switchfor controlling the passage of the current to the transformer, 15current wires leading from the transformer to the furnace and 16 aswitch for controllingthe passage of current to the furnace or muffle.The transformer is not an essential feature of the invention and may ormay not be used depending of course upon the current and the use towhich the furnace is to be applied.

The body of the furnace comprises a casing 17 whieh is preferably madeof aluminum and is detachably to a head 18 which is itself detachablysecured to the arm. At the other end of the casing a head 19 isdetachably secured. Head 19 has cast integral therewith a hearth 20 andis provided with an-opening 21 leading into the chamber 22 of thefurnace; The wall or lining of this chamber consists'of a quartz tube,indicated by 23, which is molded to the required form. Outside of thisquartz tube I provide a resistance layer 24 which consists of powderedcarborundum and powdered carbon in approximately equal proportions heldtogether by means of silicate of soda or anyv suitable binder and bakedonto the quartz tube. Outside of this resistancelayer I preferably placesuitable .non-conducting material, as for example a layer of asbestospaper. indicated by 25, and between the asbestos paper and the casingPatented Aug. 13, 1912.

a layer of furnace cement, for example orlayer is covered. by the layerof asbestos paper and that in turn is covered by the layer of furnacecement so that the energy of the current is utilized in heatingresistance layer 2 1- and the quartz lining, thereby producing a hightemperature in the chamber.

Having thus described my invention I .claimz 1. A furnace of thecharacter described comprising a quartz lining, a resistance layeroutside said lining consisting of powdered carborundum, powdered carbonand silicate of soda baked upon the lining, electrical connectionsto theresistance layer and non-conducting material outside the resist-v ancelayer. I

2. A furnace of the character described comprising a quartz lining, aresistance layer outside said lining, a layer of asbestos paper outsidethe resistance layer, an alumlnuni casing and a layer of furnace cementbetween the asbestos paper and the casing.

3. A furnace of the character described comprising a casing havingedetachable layer of the character described baked thereon, an aluminumcasing and non-coneeaeee ducting material between the resistance 10layer and the casing.

In testimony whereof I aflix my signature in presence of two Witnesses.

MANFRED J. JOHNS-0N.

"Witnesses H. H. GORTQN, EDWARD C. MILLER.

Ueptee eff this be obtained for five cents each, by addressing thetommissiener of Patents.

Washington, ID. 3,

